The purpose of the project is to further characterize the anaerobic stimulation of sugar transport that occurs in avian erythrocytes. In our earlier studies, sugar transport in these cells was found to be a passive process involving a mobile carrier. Transport was accelerated by anoxia, inhibitors of oxidative phosphorylation, and sulfhydryl blocking agents. We propose to investigate 1) the relationship between the onset of transport stimulation and changes in cell metabolites, 2) the effects of changes in the extracellular ionic environment on transport in aerobic and anaerobic cells, and 3) the effects of potential regulators on transport rate. Using the information derived from earlier studies and those proposed in this application, we propose to test models of transport regulation. Two models of regulation are described that involve an intracellular regulatory protein. Experiments to test these models are suggested.